But the greatest failing of this e-reader is the original sin of the e-book business: Almost all the titles you buy come with "digital rights management" restrictions that lock them out of competing readers. That's a distinct contrast to Amazon's excellent MP3 store, which sells standard music files you can download on the device of your choice -- or stream from Amazon in the Fire's Cloud Player app.

The Fire has also grown as a video-playback device, thanks to content deals that have added prime-time shows from Discovery Communications and Fox, among others.